Image pickup information output apparatus and lens apparatus equipped with same

ABSTRACT

Image pickup information output apparatus which outputs information about image pickup condition derived from combination of positions/states of condition decision members serving as optical members that affect fulfillment of the condition, comprising: setting unit for setting a condition setting value as the condition to be fulfilled; controller for driving one of the condition decision members to control its position/state based on the condition setting value, condition calculator for calculating information about the condition as calculated condition based on the combination of positions/states of the condition decision members; determination unit for determining whether or not the condition setting value changed; decision unit for determining the information about condition to be output, based on the calculated condition and the determination made by the determination unit as to whether or not the condition setting value changed; and output unit for outputting information about the condition to be output determined by the decision unit.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an image pickup information outputapparatus adapted to output image pickup information on an image pickupsystem which includes a lens apparatus and an image pickup apparatus,and more particularly, to an image pickup information output apparatusadapted to output image pickup information that the lens apparatus has,in the image pickup system which includes the lens apparatus and imagepickup apparatus, as well as to the lens apparatus equipped with theimage pickup information output apparatus.

Description of the Related Art

Conventionally, an image pickup information output apparatus adapted tocalculate and display object distance information, focal lengthinformation, an f-number, depth of field and an angle of view which areimage pickup conditions of a camera is disclosed in Japanese UtilityModel Application Laid-Open No. H01-78464, where the image pickupconditions are calculated from focus lens position, zoom lens positionand stop position. Also, a three-dimensional image pickup apparatus isknown which varies an optical axis angle (referred to as a convergenceangle) between left and right lenses during three-dimensionalphotography, and thereby adjusts a three-dimensional effect ofthree-dimensional video. In this case, a display control apparatus whichcalculates and records the convergence angle or a convergence distancebased on shift lens position and zoom lens position is disclosed inJapanese Patent Application Laid-Open No. 2011-135604, where theconvergence distance is a distance from an image pickup apparatus to apoint of intersection between the optical axes of the left and rightlenses and the shift lens is used for adjustment of the optical axes.

Japanese Patent Application Laid-Open No. 563-182620 discloses atechnique for automatically correcting a deviation of a focusingposition by driving a focus lens according to changes in focal length,the focus lens being a varifocal lens which varies focus lens positiondepending on zoom lens position even when an object distance, which isan image pickup condition, is constant.

Japanese Patent Application Laid-Open No. H07-306356 discloses atechnique for displaying an object distance by calculating the objectdistance from zoom lens position and an operating range of a focus lens,where the focus lens is a varifocal lens which varies focus lensposition depending on the zoom lens position even when the objectdistance, which is an image pickup condition, is constant.

It becomes sometimes necessary to output image pickup conditions of animage pickup lens, such as the object distance, f-number, focal length,depth of field, angle of view, convergence distance at a given timepoint to the outside such as to an image pickup operator. Since it isnecessary to output information about an actual state in which imagepickup is performed, when information about the image pickup conditionsare acquired from a state of a lens apparatus itself, the image pickupconditions need to be computed and found from positions of pluraloptical members including the focus lens, zoom lens, stop, and shiftlens. Furthermore, these optical members vary with plural image pickupconditions. This involves trouble because even if the image pickupconditions set by the operator is not changed, if a setting of anotherimage pickup condition is changed, image pickup condition informationwill change. To deal with this, a lens control apparatus is disclosedwhich makes automatic corrections such that even if an image pickupcondition changes, other image pickup conditions will not be affected.However, there can arise a problem in that image pickup conditioninformation will change due to calculation errors in image pickupcondition information even if image pickup conditions are fixed duringan automatic correction process if changes occur in position detectionaccuracy errors as a result of synchronization delays among pluraloptical members or changes in travel ranges of the optical members.

For example, the above problem will be described concretely by taking asan example the object distance of a varifocal lens. With a varifocallens, position of the focus lens with respect to a predetermined objectdistance is a function of zoom lens position, and thus the objectdistance can be found from the focus lens position and zoom lensposition. Therefore, in setting an object distance, a targeted focuslens position is determined from the set object distance and zoom lensposition. Furthermore, since the zoom lens position changes during thesetting of focal length, in order to keep the object distance constant,the focus lens position needs to be adjusted automatically according tothe zoom lens position. Automatic object distance adjustment such asdescribed above is disclosed in Japanese Patent Application Laid-OpenNo. S63-182620.

Furthermore, an object distance display apparatus for a varifocal lensis disclosed in Japanese Patent Application Laid-Open No. H07-306356,where the display apparatus calculates and displays an object distancebased on zoom lens position and focus lens position.

Consequently, even if the focal length changes, the object distance canbe displayed by maintaining a set object distance.

However, since the focus lens is driven and the object distance iscalculated according to zoom lens position, if there is a delay indriving the focus lens with respect to variations in zoom lens position,the focus lens cannot be moved in an instant to the focus lens positioncorresponding to targeted object distance in response to a change in thefocal length, and consequently, the object distance calculated from thezoom lens position and focus lens position deviates by the amountcorresponding to the delay in following the change in the focal length.Furthermore, the travel range of the focus lens from infinity to theclosest range varies between when the zoom lens position is on awide-angle side and when the zoom lens position is on a telephoto sidewhile position detection accuracy remains constant even when the focuslens moves, and consequently, the accuracy of object distancecorresponding to the focus lens position varies with the focal length.Therefore, since the accuracy of object distance varies with the focallength even if the object distance is the same, the object distancechanges even if the automatic object distance adjustment described aboveis carried out according to the focal length. The change in the objectdistance may cause the photographer to misunderstand that the lens ismalfunctioning. The same is similarly true for the f-number, focallength, depth of field, angle of view, convergence distance in additionto the object distance.

The conventional techniques disclosed in the patent documents describedabove do not describe how to deal with changes in object distance causedby synchronization errors of the lens or lens position detectionaccuracy.

SUMMARY OF THE INVENTION

Thus, the present invention provides an image pickup information outputapparatus for a camera, wherein when image pickup condition settings arenot changed, even if another image pickup condition setting is made, theimage pickup information output apparatus does not change image pickupcondition information as long as the change of another image pickupcondition information is within an allowable range.

To achieve the above object, the present invention provides an imagepickup information output apparatus which outputs information about animage pickup condition of a lens apparatus by driving a movable opticalmember so as to satisfy the image pickup condition, the image pickupinformation being derived from positions of a plurality of image pickupcondition decision optical members which are optical members that affectsatisfaction of the image pickup condition, the image pickup informationoutput apparatus including: a setting unit adapted to set an imagepickup condition setting value as a position of the movable opticalmember which satisfies the image pickup condition; a drive controllerfor driving a movable optical member which is one of the image pickupcondition decision optical members to control a position or state of themovable optical member based on the image pickup condition settingvalue; an image pickup condition calculator adapted to calculate theinformation about the image pickup condition as a calculated imagepickup condition based on the positions of the plurality of image pickupcondition decision optical members; a determination unit adapted todetermine whether or not there is any change in the image pickupcondition setting value; a decision unit adapted to determine imagepickup condition information to be output, based on the calculated imagepickup condition and the determination made by the determination unit asto whether or not there is any change in the image pickup conditionsetting value; and an output unit adapted to output information aboutthe image pickup condition.

The present invention can provide an image pickup information outputapparatus for a camera, wherein when image pickup condition settings arenot changed, even if another image pickup condition setting is made, theimage pickup information output apparatus does not change image pickupcondition information. This prevents the photographer frommisunderstanding that the lens is malfunctioning.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration block diagram according to a first embodiment.

FIG. 2 is a diagram illustrating a relationship among object distance(in-focus object distance), focus lens position, and zoom lens position.

FIG. 3 is a diagram illustrating a relationship between sub-targetobject distance and object distance with the elapsed time.

FIG. 4 is a diagram illustrating a relationship between sub-target focallength and zoom lens target position.

FIG. 5 is a diagram illustrating a relationship between sub-targetobject distance and focal length with the elapsed time.

FIG. 6 is a flowchart diagram illustrating procedures for detecting anychange in an object distance setting value (image pickup conditionsetting value).

FIG. 7 is a flowchart diagram illustrating procedures for determiningoutput object distance information.

FIG. 8 is a configuration block diagram according to a secondembodiment.

FIG. 9 is a diagram for illustrating convergence distance.

FIG. 10 is a diagram illustrating a relationship among convergencedistance position, shift lens position, and zoom lens position.

FIG. 11 is a diagram illustrating a relationship between sub-targetconvergence distance and convergence distance with the elapsed time.

FIG. 12 is a flowchart diagram illustrating procedures for detecting anychange in a convergence distance setting value (image pickup conditionsetting value).

FIG. 13 is a flowchart illustrating procedures for determining outputconvergence distance information.

DESCRIPTION OF THE EMBODIMENTS

preferred embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

First Embodiment

A first embodiment of the present invention will be described below withreference to FIG. 1.

FIG. 1 is a configuration block diagram according to the firstembodiment. A system illustrated by way of example in the firstembodiment includes a lens apparatus 10 adapted to control a movableoptical member related to picking up image, an object distance operatingunit 11 which is a setting unit connected to the lens apparatus 10, afocal length operating unit 12, an image pickup apparatus 13, and anexternal display apparatus 14 connected to the image pickup apparatus13.

The object distance operating unit 11 is used to operate an objectdistance (in-focus object distance) of the lens apparatus 10 and is madeup, for example, of a demand (focus demand) and a camera. The focallength operating unit 12 is used to operate focal length of the lensapparatus 10 and is made up, for example, of a demand (zoom demand) anda camera. The image pickup apparatus 13, which is, for example, acamera, is adapted to capture an object image formed by the lensapparatus 10. The external display apparatus 14 is adapted to displayimage pickup condition information such as an object distance and ismade up, for example, of a viewfinder.

The lens apparatus 10 includes a focus lens 105 used for focusadjustment and a zoom lens 115 used for zoom adjustment.

The focus lens 105 is driven under the control of a focus lens drivecontroller (drive controller) 104 made up of, for example, a controlcomputation unit and a motor. Position of the focus lens 105 is detectedby a focus lens position detector 106 made up of, for example, a Hallelement. An object distance (image pickup condition) set command valuefrom the object distance operating unit 11 is input to an objectdistance set command input unit 101. An object distance set commandvalue (image pickup condition setting value) is input to a sub-targetobject distance calculator 102, which then calculates a sub-targetobject distance which provides a target position for the object distancein each control cycle. A method of calculating the sub-target objectdistance will be described later. Based on the sub-target objectdistance and current zoom lens position, a focus lens target positioncalculator 103, which is a sub-target value calculator, calculates atarget position (movable optical member target position) of the focuslens per unit time. A method of calculating the movable optical membertarget position (the focus lens target position) will be describedlater. The focus lens drive controller 104 performs drive control suchthat the focus lens position will match a focus lens target positionvalue.

The zoom lens 115 is driven under the control of a zoom lens drivecontroller 114 made up of, for example, a control computation unit and amotor. A position of the zoom lens 115 is detected by a zoom lensposition detector 116 made up of, for example, a Hall element. A focallength set command from the focal length operating unit 12 is input to afocal length setting command input unit 111. A focal length set commandvalue is input to a sub-target focal length calculator 112, which thencalculates a sub-target focal length which provides a target positionfor the focal length in each control cycle. A method of calculating thesub-target focal length will be described later. Based on the sub-targetfocal length, a zoom lens target position calculator 113 calculates atarget position of the zoom lens per unit time. A method of calculatingthe zoom lens target position will be described later. The zoom lensdrive controller 114 performs drive control such that the zoom lensposition will match the zoom lens target position.

An object distance calculator 121 which is an image pickup conditioncalculator calculates object distance information (image pickupcondition information) as a calculated image pickup condition based onthe focus lens position from the focus lens position detector 106 andthe zoom lens position from the zoom lens position detector 116. Amethod of calculating the object distance will be described later. Aset-object-distance-change determination unit 122, which is adetermination unit, determines whether or not set object distancechanged. A method of determining whether or not set object distancechanged will be described later. An object distance decision unit 123,which is a decision unit, determines output object distance information,which is object distance information to be output to the outside. Amethod of determining the output object distance information will bedescribed later. An object distance output unit 124, which is an outputunit, outputs the output object distance information, which is outputimage pickup condition information, to the outside. According to thepresent embodiment, the output object distance information is outputfrom the object distance output unit 124 to the image pickup apparatus13.

Next, a method of calculating the focus lens target position will bedescribed.

The focus lens target position Fc can be calculated from sub-targetobject distance Dtc and zoom lens position Zp. FIG. 2 illustrates arelationship among the object distance (in-focus object distance) Dp,focus lens target position Fc, and zoom lens position Zp. The objectdistance Dp and sub-target object distance Dtc have the same units, andcan be considered to be equivalent to each other. To calculate the focuslens target position Fc, it is common practice to convertcharacteristics as illustrated in FIG. 2 into tabular data in advanceand derive the focus lens target position Fc using the object distanceDp and zoom lens position Zp as parameters. For example, if the zoomlens position Zp is Zp1 and the sub-target object distance Dtc is D1,the focus lens target position Fc is F1. Also, if the zoom lens positionZp is Zp1 and the sub-target object distance Dtc is D2, the focus lenstarget position Fc is F2.

Note that the set command value of the object distance (in-focus objectdistance) described above may not necessarily be the object distance(in-focus object distance) itself but can be a normalized value of theobject distance (in-focus object distance).

Next, a method of calculating the sub-target object distance will bedescribed.

FIG. 3 illustrates a relationship between the sub-target object distanceDtc and object distance Dp with the elapsed time when the objectdistance setting value (image pickup condition setting value) Dc changesfrom Dc1 to Dc2, where T0 represents the time at which the objectdistance setting value Dc changes from Dc1 to Dc2 and a unit time ΔTcorresponds to the duration of a control cycle. A maximum variationamount DtcMax of the sub-target object distance corresponds to a maximumstroke of the object distance Dp can cover within the unit time ΔT. Themaximum variation amount DtcMax of the sub-target object distance can becalculated based on a maximum stroke FcMax of the focus lens per unittime ΔT and tabular data which represents characteristics as illustratedin FIG. 2. For example, when the zoom lens position Zp is Zp1, if focuslens position Fp moves by the maximum stroke FcMax from F1 to F2 withinthe unit time ΔT, travel distance of the focus lens position is |F2−F1|,and |D2−D1| corresponding thereto is the maximum variation amount DtcMaxof the sub-target object distance. A value changed by the maximumvariation amount DtcMax of the sub-target object distance is calculatedevery unit time ΔT until the sub-target object distance Dtc reaches theobject distance setting value Dc2. This control allows the actual zoomlens position to keep up with a value indicated every unit time, andconsequently, stable control can be achieved without increases in thedifference between the target position and the actual position.

Next, a method of calculating the zoom lens target position will bedescribed.

Zoom lens target position Zc can be calculated from sub-target focallength Atc. FIG. 4 illustrates a relationship between the sub-targetfocal length Atc and zoom lens target position Zc. As illustrated inFIG. 4, the relationship between the focal length and zoom lens positionis represented by a linear function. To calculate the zoom lens targetposition Zc, it is common practice to actually measure the relationshipbetween the focal length and zoom lens position as illustrated in FIG.4, convert the measurements into tabular data in advance, and derive thezoom lens target position Zc. For example, when the sub-target focallength Atc is A1, the zoom lens target position Zc is Zc2.

Next, a method of calculating the sub-target focal length will bedescribed.

FIG. 5 illustrates a relationship between the sub-target focal lengthAtc and focal length Ap with the elapsed time when a focal lengthsetting value Ac changes from Ac1 to Ac2, where T0 represents the timeat which the focal length setting value Ac changes from Ac1 to Ac2 and aunit time ΔT corresponds to the duration of a control cycle. A maximumvariation amount AtcMax of the sub-target focal length corresponds to amaximum stroke of the focal length Ap within the unit time ΔT. Themaximum variation amount AtcMax of the sub-target focal length can becalculated based on a maximum stroke ZcMax of the zoom lens per unittime ΔT and tabular data which represents characteristics as illustratedin FIG. 4. Since the sub-target focal length Atc and zoom lens targetposition Zc are proportional to each other as illustrated in FIG. 4, thezoom lens target position Zc is represented by a relationship expressedin Eq. (1).Zc=(Atc×C11)+C12  (1)where C11 and C12 are predetermined constants determined from measureddata.

The maximum stroke ZcMax per unit time ΔT can be calculated from Eq.(2).ZcMax=(AtcMax×C1)+C2  (2)

A value of the sub-target focal length changed by the maximum variationamount AtcMax is calculated every unit time ΔT until the sub-targetfocal length Atc reaches the focal length setting value Ac2.

Next, a method of calculating the object distance (image pickupcondition information) will be described.

The object distance Dp can be calculated from the focus lens position Fpand zoom lens position Zp. That is, the object distance Dp (image pickupcondition information) can be calculated by use of the focus lensposition Fp and the zoom lens position Zp as a combination of theplurality of image pickup condition decision optical members. Tocalculate the object distance Dp, it is common practice to convertcharacteristics as illustrated in FIG. 2 into tabular data in advanceand derive the object distance Dp using the table. For example, when thezoom lens position Zp is Zp1 and the focus lens position Fp is F1, theobject distance Dp is D1. Also, when the zoom lens position Zp is Zp1and the focus lens position Fp is F2, the object distance Dp is D2.

As can be seen from FIG. 2, variation amounts of the focus lens positionFp relative to changes in the object distance are smaller when the zoomlens position Zp is on the wide-angle side than when the zoom lensposition Zp is on the telephoto side. Position detection accuracy of thefocus lens position Fp is equal over the entire operating range of thefocus lens, and consequently, the position detection accuracy withrespect to changes in the object distance Dp is lower when the zoom lensposition Zp is on the wide-angle side than when the zoom lens positionZp is on the telephoto side. Consequently, even if the object distancesetting value (image pickup condition setting value) is the same, theobject distance Dp has larger position errors when the zoom lensposition Zp is on the wide-angle side than when the zoom lens positionZp is on the telephoto side. Therefore, even if the set value of theobject distance is not changed, the object distance Dp computed on thewide-angle side of the zoom lens position Zp may have a different value.Thus, if the object distance Dp is displayed as it is, when zoomposition is changed, even if the object distance setting value is notchanged, the object distance Dp can change as well, causing thephotographer to misunderstand that the lens is malfunctioning.

Next, a method of determining any change in the object distance settingvalue will be described.

FIG. 6 is a flowchart illustrating procedures for detecting any changein a setting of the object distance.

Processing is started in S101, and then the flow goes to S102.

In S102, a current sub-target object distance Dtc2 is calculated, andthen the flow goes to S103.

In S103, it is determined whether or not a difference between thesub-target object distance Dtc1 stored in the previous time period andthe current sub-target object distance Dtc2 is equal to or greater thana predetermined threshold value greater than 0. If the difference isequal to or greater than the threshold value, the flow goes to S104. Ifthe difference is smaller than the threshold value, the flow goes toS106.

In S104, the current sub-target object distance Dtc2 is held for use ina next determination as a sub-target object distance Dtc1 stored in theprevious time period. Then, the flow goes to S105.

In S105, it is determined that the object distance setting valuechanged. Then, the flow goes to S107.

In S106, it is determined that the object distance setting value remainsunchanged. Then, the flow goes to S107.

In S107, the processing is finished.

In this way, it is determined whether or not the object distancesettings changed.

Although in the process of S103, the sub-target object distance Dtc isused as an instance to be determined whether or not the object distancesetting value (hereinafter, also referred to as a set-condition-changedetermination value) changed, the object distance setting value Dc maybe used as a set-condition-change determination value.

Furthermore, the focus lens target position Fc and zoom lens position Zpmay be used as set-condition-change determination values. In that case,when the focus lens target position Fc is changed with the zoom lensposition Zp remaining unchanged, it can be determined that the focuslens is driven by changes in the object distance setting value ratherthan by a focal length setting. Therefore, it may be determined that theobject distance setting value changed when an amount of change in thefocus lens target position Fc is equal to or greater than apredetermined threshold value and an amount of change in the zoom lensposition Zp is equal to or smaller than a predetermined threshold value.

Furthermore, the sub-target focal length Atc, focal length setting valueAc, zoom lens target position Zc, zoom lens position Zp or focal lengthAp may be used as a set-condition-change determination value.

In that case, when a focal length setting is being made, even if theobject distance setting value Dc does not change, the object distance Dpwill change. Therefore, if it is determined that a focal length settingis being made, processing similar to that used when there is no changein the object distance setting value is performed to prevent unnecessaryfluctuations of the object distance information output from the objectdistance output unit 124 to equipment outside the lens apparatus 10.

Furthermore, although in the present embodiment, the zoom lens is notmoved according to the object distance setting value Dc, if the zoomlens is to be moved according to the object distance setting value Dc,changes in the object distance setting value may be determined based ona relationship between the focus lens target position Fc and zoom lenstarget position Zc. In that case, when an amount of change in the objectdistance target position derived from the focus lens target position Fcand zoom lens target position Zc as well as the characteristics in FIG.2 is within a predetermined threshold value, it may be determined thatthe object distance setting value remains unchanged.

Next, a method of determining the output object distance informationwill be described. FIG. 7 is a flowchart illustrating procedures fordetermining output object distance information Dpo.

Processing is started in S201, and then the flow goes to S202.

In S202, the current object distance is calculated as the latest objectdistance Dp2, and then the flow goes to S203.

In S203, it is determined whether or not the object distance settingvalue changed. If it is determined that it changed, the flow goes toS206. If it is determined that there is no change, the flow goes toS204.

In S204, by establishing the time point at which determination as towhether or not the object distance setting value switched from “changed”to “remains unchanged” in the previous process as the start time of ano-change period, it is determined whether or not an elapsed time fromthe start time of the no-change period is equal to or longer than afixed time period Tlim1 (a first time period which is a predeterminedtime period longer than 0). A state in which the elapsed time is shorterthan the first time period is defined to be an update state and a statein which the elapsed time is equal to or longer than the first timeperiod is defined to be a preservation state. By taking control delaysbetween the sub-target object distance Dtc and object distance Dp intoconsideration, the fixed time period Tlim1 is set to the unit time ΔT.

If it is determined in S204 that the fixed time period Tlim1 haselapsed, the flow goes to S205. If it is determined that the fixed timeperiod Tlim1 has not elapsed, the flow goes to S206.

In S205, if the difference between the output object distanceinformation Dpo and the latest object distance Dp2 is equal to orgreater than a predetermined threshold value ΔDlim (equal to or greaterthan a first threshold value) greater than 0, the flow goes to S206. Ifthe difference between the output object distance information Dpo andthe latest object distance Dp2 is smaller than the predeterminedthreshold value ΔDlim (smaller than the first threshold value), the flowgoes to S208. The threshold value ΔDlim is set to a value larger than anamount of change in the object distance Dp brought about when the focallength is changed from a wide-angle end to a telephoto end, by measuringthe amount of change in advance.

In S206, the latest object distance Dp2 is held as a previous objectdistance Dp1, and then the flow goes to S207. In S207, the latest objectdistance Dp2 (first image pickup condition information) is determined tobe output object distance information Dpo (output image pickup conditioninformation), and then the flow goes to S209. In S208, the previousobject distance Dp1 (second image pickup condition information) isdetermined to be output object distance information Dpo, and then theflow goes to S209. In S209, the processing is finished.

In the process of S208, instead of the previous object distance Dp1, thesub-target object distance Dtc may be determined as output objectdistance information. Also, a driving period calculated from thedifference between the object distance setting value Dc and objectdistance Dp may be set as the fixed time period Tlim1. Furthermore,instead of the previous object distance Dp1, the object distance settingvalue Dc may be determined as the output object distance informationDpo.

Next, processes of the first embodiment will be described.

The object distance setting value Dc output from the object distanceoperating unit 11 is received by the object distance set command inputunit 101 and output to the sub-target object distance calculator 102.The sub-target object distance calculator 102 calculates the sub-targetobject distance Dtc from the object distance setting value Dc andoutputs the sub-target object distance Dtc to the focus lens targetposition calculator 103. The focus lens target position calculator 103calculates the focus lens target position Fc from the sub-target objectdistance Dtc and zoom lens position Zp and outputs the focus lens targetposition Fc to the focus lens drive controller 104. Based on the focuslens target position Fc, the focus lens drive controller 104 drives thefocus lens 105 by performing control such that the focus lens positionFp will match the focus lens target position Fc. The focus lens positiondetector 106 detects the focus lens position Fp and outputs the focuslens position Fp to the object distance calculator 121.

The focal length setting value Ac output from the focal length operatingunit 12 is received by the focal length setting command input unit 111and output to the sub-target focal length calculator 112. The sub-targetfocal length calculator 112 calculates the sub-target focal length Atcfrom the focal length setting value Ac and outputs the sub-target focallength Atc to the zoom lens target position calculator 113. The zoomlens target position calculator 113 calculates the zoom lens targetposition Zc from the sub-target focal length Atc and outputs the zoomlens drive target position Zc to the zoom lens drive controller 114.Based on the zoom lens target position Zc, the zoom lens drivecontroller 114 drives the zoom lens 115 by performing control such thatthe zoom lens position Zp will match the zoom lens target position Zc.The zoom lens position detector 116 detects the zoom lens position Zpand outputs the zoom lens position Zp to the object distance calculator121.

The object distance calculator 121 calculates the object distance(in-focus object distance)

Dp from the focus lens position Fp and zoom lens position Zp and outputsthe object distance Dp to the object distance decision unit 123. Theset-object-distance-change determination unit determines, based on thesub-target object distance Dtc, whether or not the object distancesetting value changed and outputs a result of the determination to theobject distance decision unit 123. Based on the object distance Dp aswell as on the determination result as to whether or not the objectdistance setting value changed, the object distance decision unit 123determines output object distance information (information on imagepickup conditions to be output) and outputs the output object distanceto the object distance output unit 124. The object distance output unit124 outputs the output object distance information to the image pickupapparatus 13. The image pickup apparatus 13 outputs the output objectdistance information to the external display apparatus 14.

This enables implementing an image pickup information output apparatuswhich can avoid a situation in which regardless of the object distancesetting value being not changed, the object distance information(in-focus object distance information) to be output is changed due tochanges in the focus lens position and zoom lens position or changes infocus lens position detection accuracy.

Although in the first embodiment described above, the object distancesetting value from the object distance operating unit is a positioncommand which specifies a target position, similar effects can beobtained even when a velocity command is used. This can be implementedby a method in which the object distance set command input unit 101calculates the object distance setting value Dc from reference positionand a velocity command value. For example, when the velocity commandvalue starts to be received, using the object distance Dp as a referenceposition, the object distance setting value Dc can be calculated byadding an amount of position change corresponding to the velocitycommand value to the reference position at each lapse of a unit time.

Also, although in the example described in the first embodiment, thedisplay apparatus is installed outside the lens apparatus 10, the outputobject distance information may be displayed by installing the displayapparatus in the lens apparatus 10.

Furthermore, in the example described above, the image pickup conditionis the object distance (in-focus object distance), the movable opticalmember is the focus lens, and the image pickup condition decisionoptical members are the focus lens and zoom lens, but similar effectscan be obtained when the image pickup condition to be output is depth offield and the movable optical member is a stop and the optical members(image pickup condition decision optical members) which affect thedetermination (the fulfillment) of the image pickup condition are thefocus lens, zoom lens and stop. Note that in such case, the focus lensposition, the zoom lens position and the state of stop (f-number) areused to derive the image pickup condition information (depth of field).That is, the focus lens position, the zoom lens position and the stateof stop (f-number) are used as the combination of the image pickupcondition decision optical members.

A method of calculating the depth of field Df will be described below.

The depth of field Df can be calculated from a rear depth of field Dpband front depth of field Dpf using Eq. (3), where the rear depth offield Dpb is that part of the depth of field which is located behind theobject distance Dp (on the infinity side) while the front depth of fieldis that part of the depth of field which is located in front of theobject distance Dp (on the closest side), the depth of field being arange in which the object in focus appears sharp.Df=Dpb+Dpf  (3)

Furthermore, the rear depth of field Dpb and front depth of field Dpfcan be calculated from the object distance Dp, the focal length Ap, apermissible circle of confusion σ, and an f-number Fno, using equations(4) and (5), respectively.Dpf=(σ×Fno×Dp ²)/(Ap ²+(σ×Fno×Dp))  (4)Dpb=(σ×Fno×Dp ²)/(Ap ²−(σ×Fno×Dp))  (5)Thus, the depth of field Df can be calculated using equations (3), (4)and (5).

If the depth of field Df is calculated by the above method and theobject distance is replaced with the depth of field, an image pickupinformation output apparatus can be implemented in which the depth offield is neither changed by changes in the focus lens position and zoomlens position unless the depth of field is changed intentionally nor thedepth of field is affected by changes in focus lens position detectionaccuracy.

Second Embodiment

Next, a second embodiment of the present invention will be describedwith reference to FIG. 8.

FIG. 8 is a configuration block diagram according to the presentembodiment, wherein the same components as those in FIG. 1 are denotedby the same reference numerals as the corresponding components in FIG.1.

In the second embodiment, a method of displaying a convergence distancein a three-dimensional image pickup apparatus will be described.

A lens apparatus 20 and lens apparatus 21 are adapted to control movableoptical members for the left eye and right eye, respectively, duringphotography. The lens apparatus 21 is identical in configuration to thelens apparatus 20. A convergence distance operating unit 22 serving as asetting unit is used to operate the convergence distance between thelens apparatus 20 and lens apparatus 21 and connected to the lensapparatus 20 and lens apparatus 21. The convergence distance operatingunit 22 is made up of, for example, a demand and camera. The focallength operating unit 23 is used to operate the focal length of the lensapparatus 20 and lens apparatus 21 and connected to the lens apparatus20 and lens apparatus 21. The focal length operating unit 23 is made upof, for example, a demand and camera.

The lens apparatus 20 according to the present embodiment includes ashift lens 205 and a shift lens position detector 206, where the shiftlens 205 moves in a direction having components perpendicular to opticalaxes of the respective lens apparatus to move an object image formed onan imaging surface, and thereby producing an effect equivalent to movingoptical axis directions of the lens apparatus while the shift lensposition detector 206 is made up of, for example, a Hall element.

Besides, the lens apparatus 20 according to the present embodimentincludes a convergence distance setting command input unit 201, asub-target convergence distance calculator 202, a shift lens targetposition calculator 203, a shift lens drive controller 204, aconvergence distance calculator 221 serving as an image pickup conditioncalculator, a set-convergence-distance-change determination unit 222, aconvergence-distance decision unit 223 and a convergence distance outputunit 224.

The convergence distance setting command input unit 201 receives aconvergence distance setting value (image pickup condition settingvalue) from outside and the sub-target convergence distance calculator202 calculates a sub-target convergence distance which provides a targetposition for the convergence distance in each control cycle based onconvergence distance setting value received by the convergence distancesetting command input unit 201. A method of calculating the sub-targetconvergence distance will be described later. Based on the sub-targetconvergence distance and current zoom lens position, the shift lenstarget position calculator 203, which is a sub-target value calculator,calculates a target position of the shift lens per unit time. A methodof calculating the shift lens target position will be described later.The shift lens drive controller 204, which is made up of, for example, acontrol computation unit and a motor, performs drive control such thatthe shift lens position will match the shift lens target position.

The convergence distance calculator 221 calculates the convergencedistance based on the shift lens position and zoom lens position. Amethod of calculating the convergence distance will be described later.The set-convergence-distance-change determination unit 222 serving as adetermination unit determines whether or not the convergence distancesetting value changed. A method of determining whether or not theconvergence distance setting value changed will be described later. Theconvergence distance decision unit 223 serving as a decision unitdetermines convergence distance information to be output to the outside.A method of determining output convergence distance information will bedescribed later. The convergence distance output unit 224 serving as anoutput unit outputs the convergence distance information, which isoutput image pickup condition information, to the outside.

Next, convergence distance will be described.

FIG. 9 is a diagram illustrating a relationship among a field lens L, afield lens R, the convergence distance Cp, base length a, an opticalaxis VL, an optical axis VR, a convergence point p and a convergenceangle θ. The optical axis VL is the optical axis of the lens apparatus20 while the optical axis VR is the optical axis of the lens apparatus21. The base length a is an interval between the optical axes in theimage pickup apparatus, and specifically, is a distance between a centerof the field lens L and a center of the field lens R. The convergencepoint p is a point at which the optical axes VL and VR intersect eachother. The convergence angle θ is an angle formed by the optical axes VLand VR intersecting each other at the convergence point p. Theconvergence distance Cp is the distance from a line joining the fieldlens L and field lens R of the left and right image pickup apparatusesto the convergence point p.

As illustrated in FIG. 9, the lens apparatus 20 and lens apparatus 21perform control to drive the shift lenses 205 in opposite directionssuch that the optical axes VL and VR will move in the oppositedirections and intersect each other at the convergence point p.

A relationship among the convergence distance Cp, base length a andconvergence angle θ is given by Eq. (6).Cp=(a/2)/tan(θ/2)  (6)

If video shot with the convergence distance Cp is projected onto ascreen, a viewer can view three-dimensional video by visually perceivingthe video from the lens apparatus 20 with the left eye and the videofrom the lens apparatus 21 with the right eye. In this case, if theconvergence distance Cp which is the distance to the convergence pointgiven as a point of intersection between the optical axes VL and VR isshorter than the distance from the viewer to the screen, the viewerfeels as if the object were located in front of the screen and if theconvergence distance Cp is longer than the distance from the viewer tothe screen, the viewer feels as if the object were located behind thescreen.

Next, a method of calculating the shift lens target position will bedescribed.

The shift lens target position Sc can be calculated from the sub-targetconvergence distance Ctc and zoom lens position Zp. FIG. 10 illustratesa relationship among the convergence distance position Cp, shift lenstarget position Sc, and zoom lens position Zp. The convergence distanceposition Cp and sub-target convergence distance Ctc have the same units,and can be considered to be equivalent to each other. To calculate theshift lens target position Sc, it is common practice to convertcharacteristics as illustrated in FIG. 10 into tabular data in advanceand derive the shift lens target position Sc. For example, if the zoomlens position Zp has a value of Zp1 and the sub-target convergencedistance Ctc has a value of C1, the shift lens target position Sc has avalue of S1. Also, if the zoom lens position Zp has a value of Zp1 andthe sub-target convergence distance Ctc has a value of C2, the shiftlens target position Sc has a value of S2.

With reference to a position at which the optical axis VL and opticalaxis VR are parallel to each other, the lens apparatus 21 is controlledso as to move the optical axis VL by the same amount at the same angleas the optical axis VR in a direction opposite to the optical axis VR ofthe lens apparatus 20.

As can be seen from FIG. 10, amounts of change in the shift lensposition Sp relative to changes in the convergence distance are smallerwhen the zoom lens position Zp is on the wide-angle side than when thezoom lens position Zp is on the telephoto side. Position detectionaccuracy of the shift lens position Sp is equal over the entireoperating range of the shift lens, and consequently, the positiondetection accuracy with respect to changes in the convergence distanceCp is lower when the zoom lens position Zp is on the wide-angle sidethan when the zoom lens position Zp is on the telephoto side.Consequently, even if the convergence distance setting value is thesame, the convergence distance Cp has larger amounts of position errorwhen the zoom lens position Zp is on the wide-angle side than when thezoom lens position Zp is on the telephoto side. Therefore, theconvergence distance Cp computed on the wide-angle side of the zoom lensposition Zp may have a different value. Thus, displaying the convergencedistance Cp with no change may cause the photographer to misunderstandthat the lens is malfunctioning because changing zoom position causesthe convergence distance Cp changed regardless of the convergencedistance setting value being not changed.

Next, a method of calculating the sub-target convergence distance willbe described.

FIG. 11 illustrates a relationship between the sub-target convergencedistance Ctc and convergence distance Cp with the elapsed time when aconvergence distance setting value (image pickup condition settingvalue) Cc changes from Cc1 to Cc2, where T0 represents the time at whichthe convergence distance setting value Cc changes from Cc1 to Cc2 and aunit time ΔT corresponds to the duration of a control cycle. A maximumvariation amount CtcMax of the sub-target convergence distancecorresponds to a maximum stroke of the convergence distance Cp withinthe unit time ΔT. The maximum variation amount CtcMax of the sub-targetconvergence distance can be calculated based on a maximum stroke ScMaxof the shift lens per unit time ΔT and tabular data which representscharacteristics as illustrated in FIG. 10. For example, when the zoomlens position Zp is Zp1 and the shift lens position Sp is S1, if themaximum stroke ScMax is |S2−S1|, then the maximum variation amountCtcMax of the sub-target convergence distance is |C2−C1|. A valuechanged by the maximum variation amount CtcMax of the sub-targetconvergence distance is calculated every unit time ΔT until thesub-target convergence distance Ctc reaches the convergence distancesetting value Cc2.

Next, a method of detecting changes in the convergence distance settingvalue will be described.

FIG. 12 is a flowchart illustrating procedures for detecting any changein the convergence distance setting value.

Processing is started in S301, and then the flow goes to S302.

In S302, current sub-target convergence distance Ctc2 is calculated, andthen the flow goes to S303.

In S303, it is determined whether or not a difference between thesub-target convergence distance Ctc1 stored in the previous time periodand the current sub-target convergence distance Ctc2 is equal to orgreater than a predetermined threshold value greater than 0. If thedifference is equal to or greater than the threshold value, the flowgoes to S304. If the difference is smaller than the threshold value, theflow goes to S306.

In S304, the current sub-target convergence distance Ctc2 is held foruse in a next determination as a sub-target convergence distance Ctc1stored in the previous time period. Then, the flow goes to S305.

In S305, it is determined that the convergence distance setting valuechanged. Then, the flow goes to S307.

In S306, it is determined that the convergence distance setting valueremains unchanged. Then, the flow goes to S307.

In S307, the processing is finished.

In this way, any change in the convergence distance setting value isdetected.

Although in the process of S302, the sub-target convergence distance Ctcis used as an instance to be determined whether or not the convergencedistance setting value changed, the convergence distance setting valueCc may be used as an instance to be checked for the change.

Furthermore, the shift lens target position Sc and zoom lens position Zpmay be used as the instances to be checked for the change. In that case,when the shift lens target position Sc is changed with the zoom lensposition Zp remaining unchanged, it can be determined that the shiftlens is driven by changes in the convergence distance setting valuerather than by a focal length setting. Therefore, it may be determinedthat there is a change in the convergence distance setting value when anamount of change in the shift lens target position Sc is equal to orgreater than a predetermined threshold value (equal to or greater than asecond threshold value) greater than 0 and an amount of change in thezoom lens position Zp is equal to or smaller than a predeterminedthreshold value (equal to or smaller than a third threshold value)greater than 0.

Furthermore, the sub-target focal length Atc, focal length setting valueAc, zoom lens target position Zc, zoom lens position Zp or focal lengthAp may be used as the instance to be checked for the change.

In that case, when a focal length setting is being made, even if theconvergence distance setting value Cc does not change, the convergencedistance Cp will change. Therefore, if it is determined that a focallength setting is being made, processing similar to that used when theconvergence distance setting value remains unchanged is performed toprevent unnecessary fluctuations of the convergence distance Cp, whichis the convergence distance information output from the convergencedistance output unit 224 to equipment outside the lens apparatus 20.

Furthermore, although in the present embodiment, the zoom lens positionis not moved according to the convergence distance setting value Cc, ifthe zoom lens position is to be moved according to the convergencedistance setting value Cc, changes in the convergence distance settingvalue may be determined based on a relationship between the shift lenstarget position Sc and zoom lens target position Zc. In that case, whenan amount of change in the convergence distance target position derivedfrom the shift lens target position Sc and zoom lens target position Zcas well as the characteristics in FIG. 2 is within a predeterminedthreshold value greater than 0, it may be determined that there is nochange in the convergence distance setting value.

Next, a method of determining the output convergence distanceinformation will be described.

FIG. 13 is a flowchart illustrating procedures for determining outputconvergence distance information Cpo.

Processing is started in S401, and then the flow goes to S402.

In S402, current convergence distance is calculated as the latestconvergence distance Cp1, and then the flow goes to S403.

In S403, it is determined whether or not the convergence distancesetting value changed. If it is determined that the convergence distancesetting value changed, the flow goes to S406. If it is determined thatthe convergence distance setting value remains unchanged, the flow goesto S404.

In S404, by establishing the time point at which determination as towhether or not the convergence distance setting value changed switchedfrom “changed” to “remains unchanged” in the previous process as thestart time of a no-change period, it is determined whether or not anelapsed time from the start time of the no-change period is equal to orlonger than a fixed time period Tlim2.

By taking control delays between the sub-target convergence distance Ctcand convergence distance Cp into consideration, the fixed time periodTlim2 is set to the unit time ΔT.

If it is determined in S404 that the fixed time period Tlim2 haselapsed, the flow goes to S405. If it is determined that the fixed timeperiod Tlim2 has not elapsed, the flow goes to S406.

In S405, if the difference between the output convergence distanceinformation Cpo and the latest convergence distance Cp2 is equal to orgreater than a predetermined threshold value ΔClim (equal to or greaterthan a first threshold value) greater than 0, the flow goes to S406. Ifthe difference between the output convergence distance information Cpoand the latest convergence distance Cp2 is smaller than thepredetermined threshold value ΔClim (smaller than the first thresholdvalue), the flow goes to S408. The threshold value ΔClim is set to avalue larger than an amount of change in the convergence distance Cpbrought about when the focal length is changed from the wide-angle endto the telephoto end, by measuring the amount of change in advance.

In S406, the latest convergence distance Cp2 is held as a previousconvergence distance Cp1, and then the flow goes to S407. In S407, thelatest convergence distance Cp2 (first image pickup conditioninformation) is determined to be output convergence distance informationCpo (output image pickup condition information), and then the flow goesto S409. In S408, the previous convergence distance Cp1 (second imagepickup condition information) is determined to be output convergencedistance information Cpo, and then the flow goes to S409. In S409, theprocessing is finished.

In the process of S408, instead of the previous convergence distanceCp1, convergence distance target position Cpc may be determined asoutput convergence distance information. Also, a driving periodcalculated from the difference between the convergence distance settingvalue Cc and convergence distance Cp may be set as the fixed time periodTlim2. Furthermore, instead of the previous convergence distance Cp1,the convergence distance setting value Cc may be determined as theoutput convergence distance information Cpo.

Next, processes of the second embodiment will be described.

The convergence distance setting value Cc output from the convergencedistance operating unit 22 is received by the convergence distancesetting command input unit 201 and output to the sub-target convergencedistance calculator 202. The sub-target convergence distance calculator202 calculates the sub-target convergence distance Ctc from theconvergence distance setting value Cc and outputs the sub-targetconvergence distance Ctc to the shift lens target position calculator203. The shift lens target position calculator 203 calculates the shiftlens target position Sc from the sub-target convergence distance Ctc andzoom lens position Zp and outputs the shift lens target position Sc tothe shift lens drive controller 204. Based on the shift lens targetposition Sc, the shift lens drive controller 204 controls to drive theshift lens 205 so that the shift lens position Sp matches the shift lenstarget position Sc. The shift lens position detector 206 detects theshift lens position Sp and outputs the shift lens position Sp to theconvergence distance calculator 221.

The focal length setting value Ac output from the focal length operatingunit 23 is received by the focal length setting command input unit 111and output to the sub-target focal length calculator 112. The sub-targetfocal length calculator 112 calculates the sub-target focal length Atcfrom the focal length setting value Ac and outputs the sub-target focallength Atc to the zoom lens target position calculator 113. The zoomlens target position calculator 113 calculates the zoom lens targetposition Zc from the sub-target focal length Atc and outputs the zoomlens target position Zc to the zoom lens drive controller 114. Based onthe zoom lens target position Zc, the zoom lens drive controller 114controls to drive the zoom lens 115 so that the zoom lens position Zpmatch the zoom lens target position Zc. The zoom lens position detector116 detects the zoom lens position Zp and outputs the zoom lens positionZp to the convergence distance calculator 221.

The convergence distance calculator 221 calculates the convergencedistance Cp based on the shift lens position Sp and zoom lens positionZp and outputs the convergence distance Cp to the convergence distancedecision unit 223. That is, the convergence distance Cp (image pickupcondition information) can be calculated by use of the shift lensposition Sp and the zoom lens position Zp as a combination of theplurality of image pickup condition decision optical members. Theset-convergence-distance-change determination unit determines, based onthe sub-target convergence distance Ctc, whether or not the convergencedistance setting value changed and outputs a result of the determinationto the convergence distance decision unit 223. Based on the convergencedistance Cp as well as on the determination result as to whether or notconvergence distance setting value changed, the convergence distancedecision unit 223 determines output convergence distance information andoutputs the output convergence distance information to the convergencedistance output unit 224. The convergence distance output unit 224outputs the output convergence distance information to the image pickupapparatus 13. The image pickup apparatus 13 outputs the outputconvergence distance information to the external display apparatus 14.

This enables implementing an image pickup information output apparatuswhich can avoid a situation in which the convergence distanceinformation to be output is changed due to changes in the shift lensposition and zoom lens position or changes in shift lens positiondetection accuracy regardless of the convergence distance setting valueremaining unchanged.

Although in the present embodiment, a shift lens for optical axisadjustment is used to control the convergence distance, a variable apexangle prism may be used instead of the shift lens. Alternatively,similar effects can be obtained if the angle formed by the optical axesof the two lens apparatuses is directly controlled by mechanicallypanning each of the two lens apparatuses.

In the configurations illustrated by way of example in the aboveembodiments, operating units such as the object distance operating unit11, focal length operating units 12 and 23, and convergence distanceoperating unit 22 are provided on cameras and demands, the externaldisplay apparatus 14 is connected to the image pickup apparatus 13, andthe other components are included in the lens apparatuses 10 and 20.However, the present invention is not limited to this. Except opticalcomponents such as the lenses and stop as well as drive controllers andposition detectors therefor, the components included in the lensapparatus 10 or 20 illustrated in FIG. 1 or 8 may be provided onapparatuses except the lens apparatus, for example, in a console device,camera, or independent control apparatus. Conversely, although operatingunits such as the object distance operating unit 11, focal lengthoperating units 12 and 23, and convergence distance operating unit 22 aswell as the external display apparatus have been described as beinginstalled outside the lens apparatus, this is not restrictive, andeffects of the present invention can be achieved similarly even if thesecomponents are installed in the lens apparatus. Although the convergencedistance is exemplified as the image pickup condition in the secondembodiment described above, the convergence angle can be used as theimage pickup condition to obtain the advantageous effect of the presentinvention.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments and that variousmodifications and changes can be made within the scope of the invention.The scope of the following claims is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures and functions.

This application claims the benefit of Japanese Patent Application No.2011-219535, filed Oct. 3, 2011, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An information output apparatus, comprising: asetting unit configured to set an object distance setting value; aderiving unit configured to derive object distance information based ona position of a focus lens and a position of a zoom lens; adetermination unit configured to determine whether or not the objectdistance setting value changed; and an output unit configured to outputthe object distance information derived by the deriving unit based on adetermination made by the determination unit, wherein the output unitupdates the object distance information to be output when thedetermination unit determines the setting value being changed, and doesnot update the object distance information to be output when thedetermination unit does not determine the setting value being changed.2. The information output apparatus according to claim 1, configuredsuch that: the determination unit determines whether or not the objectdistance setting value changed based on a set-condition-changedetermination value representing a change in the object distance settingvalue; and the output unit updates the object distance information to beoutput when a state from a time when the determination unit determinesthat the object distance setting value changed until a first time periodelapses is determined as an update state and does not update the objectdistance information to be output when a state other than the updatestate is determined as a preservation state.
 3. The information outputapparatus according to claim 2, configured such that: the determinationunit determines whether or not the object distance setting value changedbased on a set-condition-change determination value representing achange in the object distance setting value; the output unit determinesa state from a time when the determination unit determines that theobject distance setting value changed until a first time period elapsesto be an update state and determines a state other than the update stateto be a preservation state; and the output unit updates the objectdistance information to be output in the update state, while in thepreservation state, the output unit updates the object distanceinformation to be output when a difference between the object distanceinformation and a past object distance information derived before theobject distance information started to change is equal to or greaterthan a first threshold value and does not update the object distanceinformation to be output when the difference is smaller than the firstthreshold value.
 4. The information output apparatus according to claim3, wherein the first threshold value is greater than an amount of changeof the object distance information when the object distance settingvalue is not changed.
 5. An information output apparatus, comprising: asetting unit configured to set an object distance setting value; aderiving unit configured to derive object distance information based ona position of a focus lens and a position of a zoom lens; adetermination unit configured to determine whether or not the objectdistance setting value changed; and an output unit configured to outputthe object distance information derived by the deriving unit based on adetermination made by the determination unit, wherein the output unitoutputs the object distance information when the determination unitdetermines the setting value being changed, and outputs a past objectdistance information derived before the object distance informationstarted to change when the determination unit does not determine thesetting value being changed.
 6. The information output apparatusaccording to claim 5, configured such that: the determination unitdetermines whether or not the object distance setting value changedbased on a set-condition-change determination value representing achange in the object distance setting value; the output unit determinesa state from a time when the determination unit determines that theobject distance setting value changed until a first time period elapsesas an update state and determines a state other than the update state asa preservation state; and the output unit outputs the object distanceinformation in the update state while outputs the past object distanceinformation in the preservation state.
 7. The information outputapparatus according to claim 5, configured such that: the determinationunit determines whether or not the object distance setting value changedbased on a set-condition-change determination value representing achange in the object distance setting value; the output unit determinesa state from a time when the determination unit determines that theobject distance setting value changed until a first time period elapsesto be an update state and determines a state other than the update stateto be a preservation state; and the output unit outputs the objectdistance information in the update state, while in the preservationstate, the output unit outputs the object distance information when adifference between the object distance information and the past objectdistance information is equal to or greater than a first threshold valueand outputs the past object distance information when the difference issmaller than the first threshold value.
 8. The information outputapparatus according to claim 5, wherein the first threshold value isgreater than an amount of change of the object distance information whenthe object distance setting value is not changed.
 9. A lens apparatuscomprising: a focus lens; a zoom lens; and an information outputapparatus, comprising: a setting unit configured to set an objectdistance setting value; a deriving unit configured to derive objectdistance information based on a position of a focus lens and a positionof a zoom lens; a determination unit configured to determine whether ornot the object distance setting value changed; and an output unitconfigured to output the object distance information derived by thederiving unit based on a determination made by the determination unit,wherein the output unit updates the object distance information to beoutput when the determination unit determines the setting value beingchanged, and does not update the object distance information to beoutput when the determination unit does not determine the setting valuebeing changed.
 10. An image pickup apparatus system comprising: a lensapparatus including a focus lens and a zoom lens; an image pickupapparatus configured to capture an object image formed by the lensapparatus; an information output apparatus, comprising: a setting unitconfigured to set an object distance setting value; a deriving unitconfigured to derive object distance information based on a position ofa focus lens and a position of a zoom lens; a determination unitconfigured to determine whether or not the object distance setting valuechanged; and an output unit configured to output the object distanceinformation derived by the deriving unit based on a determination madeby the determination unit, wherein the output unit updates the objectdistance information to be output when the determination unit determinesthe setting value being changed, and does not update the object distanceinformation to be output when the determination unit does not determinethe setting value being changed; and a display apparatus configured todisplay the object distance information.
 11. A lens apparatuscomprising: a focus lens; a zoom lens; and an information outputapparatus, comprising: a setting unit configured to set an objectdistance setting value; a deriving unit configured to derive objectdistance information based on a position of a focus lens and a positionof a zoom lens; a determination unit configured to determine whether ornot the object distance setting value changed; and an output unitconfigured to output the object distance information derived by thederiving unit based on a determination made by the determination unit,wherein the output unit outputs the object distance information when thedetermination unit determines the setting value being changed, andoutputs a past object distance information derived before the objectdistance information started to change when the determination unit doesnot determine the setting value being changed.
 12. An image pickupapparatus system comprising: a lens apparatus including a focus lens anda zoom lens; an image pickup apparatus configured to capture an objectimage formed by the lens apparatus; an information output apparatus,comprising: a setting unit configured to set an object distance settingvalue; a deriving unit configured to derive object distance informationbased on a position of a focus lens and a position of a zoom lens; adetermination unit configured to determine whether or not the objectdistance setting value changed; and an output unit configured to outputthe object distance information derived by the deriving unit based on adetermination made by the determination unit, wherein the output unitoutputs the object distance information when the determination unitdetermines the setting value being changed, and outputs a past objectdistance information derived before the object distance informationstarted to change when the determination unit does not determine thesetting value being changed; and a display apparatus configured todisplay the object distance information.
 13. An information outputapparatus, comprising: a setting unit configured to set a setting valueof an f-number, a deriving unit configured to derive f-numberinformation based on a position of a stop and a position of a zoom lens;a determination unit configured to determine whether or not the settingvalue is changed; and an output unit configured to output the f-numberinformation derived by the deriving unit based on a determination madeby the determination unit, wherein the output unit updates the f-numberinformation to be output when the determination unit determines thesetting value being changed, and does not update the f-numberinformation to be output when the determination unit does not determinethe setting value being changed.
 14. An information output apparatus,comprising: an operating unit that operates a focus lens to change anobject distance to be focused; a deriving unit that derives objectdistance information based on a position of the focus lens and aposition of a zoom lens; and an output unit configured to output theobject distance information derived by the deriving unit, wherein theoutput unit outputs the object distance information without beingchanged when a position of the zoom lens is changed and the operatingunit is not operated.